Loans and Allowance for Loan Losses (Details 10) - USD ($) $ in Millions	Jun. 30, 2016		Dec. 31, 2015
Pre- and Post - modification recorded investments
Commitment to lend additional funds to borrowers with loan modifications classified as TDRs	$ 57		$ 98
Total excluding purchased credit-impaired loans	635	[1]	822
Commercial portfolio
Pre- and Post - modification recorded investments
Total excluding purchased credit-impaired loans	348		515
Commercial portfolio | Commercial and industrial
Pre- and Post - modification recorded investments
Total excluding purchased credit-impaired loans	333		499
Commercial portfolio | Commercial mortgage
Pre- and Post - modification recorded investments
Total excluding purchased credit-impaired loans	15		16
Consumer portfolio
Pre- and Post - modification recorded investments
Total excluding purchased credit-impaired loans	287		307
Consumer portfolio | Residential mortgage
Pre- and Post - modification recorded investments
Total excluding purchased credit-impaired loans	256		276
Consumer portfolio | Home equity and other consumer loans
Pre- and Post - modification recorded investments
Total excluding purchased credit-impaired loans	$ 31		$ 31

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